Flyweight



A. N. PEALE Jan. 14, 1969 FLYWEIGHT Sheet Filed March 15, 1966 IINVENTOR ALFRED N. PE'ALE ATTORNEY I Jan. 14, 1969 A. N. PEALE 3,421,414

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ATTORNEY United States Patent Office 3,421,414- Patented Jan. 14, 1969 6Claims ABSTRACT OF THE DISCLOSURE A motor speed control mechanismincluding a variable speed motor, a valve controlling the supply ofenergy to the motor, a radially movable fiyweight pivoted on the rotaryshaft of the motor and a linkage interconnecting the fiyweight to thevalve to vary the speed of the motor in response to the radial movementof the fiyweight. The fiyweight includes a bore arranged with one endbeing closer to the axis of the fiyweight pivot and the other end beingcloser to the axis of the shaft in the retracted position of thefiyweight. A weight is movably enclosed in the bore whereby the weightis urged by the centrifugal force to the one end of the bore in theretracted position of the fiyweight and to the other end of the bore inthe extended position of the fiyweight resulting in the center ofgravity of the fiyweight shifting away from the fiyweight pivot as thefiyweight moves radially outward toward its extended position.

This invention relates to motor speed control systems usingcentrifugally actuated flyweights as speed sensing means.

In certain applications, it is desirable that the speed of a motor bemaintained within a relatively narrow speed range. In general,conventional speed control systems using fiyweights do not controlspeeds within a relatively narrow speed range, particularly, when theflyweights are retracted by strong springs.

The primary object of this invention is to substantially overcome orminimize the above disadvantages in conventional speed control systemsof the fiyweight type.

Further important objects of this invention are: to provide a fiyweightspeed control system which maintains motor speeds within a relativelynarrow speed range; to provide a rapid acting fiyweight speed controlsystem; to provide an improved fiyweight for use in speed controlsystems; and to provide a fiyweight speed control system which abruptlyshifts the forces acting on a fiyweight at some point during its normaloperation.

The foregoing objects are attained, in general, by the provision of afiyweight speed control system having pivoted flyweights with means forabruptly changing the centrifugal torque acting on the flyweights atsome point intermediate the limits of pivoting movement of theflyweights. This is accomplished by providing each fiyweight with ameans which acts to shift the center of gravity of the fiyweight at apredetermined speed of the shaft or motor driving the fiyweight. Thisshift in the center of gravity is caused by the centrifugal force actingon the fiyweight.

The invention is described in connection with the accompanying drawingswherein:

FIG. 1 is an elevational view with portions shown in section of anair-powered grinder tool utilizing the improved speed control system ofthis invention;

FIG. 2 is an enlarged fragment of FIG. 1 illustrating the flyweights andwith one of the flyweights being sectioned to show its interior;

FIG. 3 is similar to FIG. 2 and shows plural positions of the flyweightsduring operation of the tool of FIG. 1;

FIG. 4 is a diagrammatic view illustrating the shift of the center ofgravity of a fiyweight;

FIG. 5 is a graph or curve illustrating the centrifugal torque forcesacting on a fiyweight in relation to its speed; and

FIG. 6 is an elevational view with a portion cut away illustrating amodified embodiment of fiyweight.

The air powered grinder 1 shown in FIG. 1 comprises a casing 2 includinga handle 3 and a head cover 4. The casing 2 contains a conventionalair-powered motor 5 having a rotor 6 driving a spindle 7. The spindle 7carries a grinder wheel 8 rotating within a stationary shield 9 fixed tothe casing 2.

The end of the handle 3 is provided with an inlet 11 adapted to beconnected to an air supply hose (not shown). The inlet 11 leads to aconventional throttle valve 12 mounted in the forward part of the handle3. When manually opened, the throttle valve 12 feeds air to a speedcontrol valve 13 which acts to throttle and vary the quantity of airdelivered to the motor 5 for controlling and limiting the speed of themotor '5.

The speed control valve 13 includes a valve sleeve 14 carried in thecasing 2 and having an air inlet 15- at one end and an air outlet 16extending through its sidewall. A valve piston 17 reciprocates in thevalve sleeve 14 in a manner to vary the effective area of the air outlet16. The valve piston 17 includes a piston rod 18 which slidably extendsthrough the upper end of the valve sleeve 14, as shown in FIG. 1, foroperating the valve piston 17. The valve piston 17 is urged upwardly in.the valve sleeve 14 by a spring 10.

A fiyweight-type of governor 19 is carried by the upper end of the motorrotor 6 and includes a cap plate 20 attached to the end of the motorrotor 6 and a pair of L-shaped fiyweight 21 pivoted at 22 on the capplate 20. Looking at FIG. 1, each fiyweight 21 includes a foot 23 and aleg 24 extending upwardly from the foot 23 at a right angle. Thegovernor 19 further includes an axial plunger 25 slidably mounted in thecap plate 20 and extending into a cavity provided in the motor rotor 6.The plunger 25 includes a head 26 at its upper end resting on the feet23 of the fiyweights 21 and a nut 27 threaded at its lower end. A spring28 is interposed between the nut 27 and the cap plate 20 to urge theplunger head 26 downwardly against the fiyweights 21 for biasing themradially inward.

As is conventional in fiyweight-type speed control systems, as the motorspeed increases, centrifugal force acting on the flyweights 21 serves tolift the plunger 25 upwardly, as seen in FIG. 1, against the force ofthe spring 28. The vertical upward movement of the plunger 25 istransmitted to the speed control piston rod 18 by a bell crank 29pivoted on a pivot 30 fixed in the head cover 4 and having opposite armsresting respectively on the plunger head 26 and the piston rod 18. Allof the foregoing structure is conventional, as shown in United StatesPatent No. 2,897,832.

The invention in this application is the concept of pro viding each ofthe flyweights 21 with a means which abruptly shifts the center ofgravity of the fiyweights outwardly from the pivot axis 22 of thefiyweight at some point intermediate the limits of the pivot travel ofthe fiyweights. This expedient is carried out in FIGS. 2 and 3 byproviding the legs 24 of each of the flyweights 21 with an elongatedbore 32 having a ball 33 which can readily roll or shift between theopposite ends of the bore 32. The outer end of the bore 32 is closed bya plug 34 for trapping the ball 33 therein.

The axis 35 of the bore 32 is arranged so that, when the flyweights 21are at rest in their retracted positions with the fiyweight feet 23resting on the cap plate 20, as

shown in FIG. 2, the outer end 37 of each bore 32 remote from theflyweight pivot 22, is closer to the motor axis 36 than the inner end 38of the bore 32. In this position of the flyweights 21, centrifugal forcewill maintain the ball in the inner end 38 of the bore 32, as shown inFIG. 2. As centrifugal force on the flyweights increases, the flyweightswill pivot outwardly to a position where the axis 35 of the bore 32pivots through a line parallel with the motor axis 36, as shown in FIG.3. In the latter position of the flyweights, each bore axis 35 isarranged with the outer end 37 of the bore 32 further away from themotor axis 36 than its inner end 38, and the ball 33 is forced to theouter end 37 of the bore 32 by centrifugal force. This movement of theball 33 shifts the center of gravity of the flyweights 21 radiallyoutward from the flyweight pivot 22. Shifting the center of gravity ofthe flyweights 21 radially away from the flyweight pivot 22 increasesthe torque or moment forcing the flyweights 21 radially outward abouttheir pivots 22. This shift in center of gravity occurs relativelyabruptly as the ball 33 shifts from one end of the bore 32 to the other.The amount of the shift in the center of gravity depends on the weightof the ball 33 and the length of the bore 32.

The abrupt shift in the center of gravity of the flyweight 21 as itpivots radially outwardly about its pivot axis 22 is illustrated inFIGS. 4 and 5. Initially, when the ball 33 is located in the inner end38 of the bore 32, looking at FIG. 4, the center of gravity of theflyweight 21 is located at C6 It will be understood that the center ofgravity of the flyweight is determined by the combination of its massplus the mass of the ball 33. At this time the centrifugal force Facting on the flyweight is acting through C6 The moment arm of thecentrifugal force F acting about the pivot 22 is indicated as L Thetorque or moment of the flyweight 21 is the product of F L As explainedearlier, as the motor speed increases, the flyweight 21 is forced topivot radially outward about its pivot 22 by centrifugal force. Theflyweight bore 32 eventually reaches a position relative to the motoraxis 36 wherein the centrifugal force acting on the ball 33 forces itoutward in the bore 32 to the outer end 37 of the bore, as shown indotted lines in FIG. 4. When the ball 33 reaches the dotted lineposition shown in FIG. 4, the center of gravity of the flyweight 21 isshifted away from the flyweight pivot 22 to the position indicated as 06At this time the centrifugal force F acts through CG and the moment armof F about the pivot 22 is L Now the torque or moment of F is F XL SinceCG is at a greater distance from the pivot 22 than CG F L is greaterthan F L The result of the shift in the center of gravity of theflyweight is further shown in FIG. 5. FIG. is a curve having a verticalaxis indicating the torque of the flyweight 21 about its axis 22 and ahorizontal axis indicating the speed of the flyweight 21 about the motoraxis 36. The initial portion of the curve, rising from zero torque,indicates the change in the initial torque, F L This torque varies inaccordance with the increase in centrifugal force as the rotary speed ofthe flyweight 21 increases. As is well known, the centrifugal forceacting on the flyweight will increase relative to the square of thespeed of the flyweight.

The abrupt vertical leg of the curve indicates the shift of the ce terof gravity of the flyweight 21 from CG to CG due to the movement of theball 33 between the ends of the bore 32. The final leg of the curveillustrates the torque F L which acts about the center of gravity CG Thecurve in FIG. 5 further includes a dotted line indicating the nature ofthe torque curve if the shift in center of gravity had not occurred. Asis easily seen from this, the shift in center of gravity of theflyweight 21 causes a substantial change in the value of the torque acting on the flyweight 21 about its pivot 22.

It has been found that the provision of this abrupt change in torqueacting on the flyweight 21 results in causing the speed control means toregulate and maintain the speed of the motor within a much narrowerspeed range than is possible without the abrupt change of flyweighttorque. The disclosed abrupt torque change means is particularlynecessary in flyweight speed control systems when relatively strongsprings are used for retracting the flyweights.

A second embodiment of the invention is shown in FIG. 6. The onlydifference between this embodiment and the earlier embodiment is theaddition of a light spring 40 to the bore 32 serving to bias the ball 33toward the inner end 38 of the bore. The spring 40 is so light or weakthat it does not substantially interfere with the movement of the ball33 to the outer end 37 of the bore 32 during operation of the flyweight21. The only purpose of the spring 40 is to insure that the ball 33remains in the inner end 38 of the bore 32 at low speeds when thegrinding tool 1 is placed in a position where gravity might otherwisemove the ball 33 to the outer end 37 of the bore 32.

Although two embodiments of the invention are illustrated and describedin detail, it will be understood that the invention is not limitedsimply to these embodiments but contemplates other embodiments andvariations which utilize the concepts and teachings of this invention.

Having described my invention, 1 claim:

1. A motor speed control system comprising:

a rotary motor;

variable valve means for supplying energy to said motor and includingmeans urging it to an open position;

a flyweight pivoted on a shaft driven by said motor and movable betweena retracted position and an extended position;

means interconnecting said flyweight to said valve means forprogressively closing said valve means as said flyweight moves from saidretracted position to said extended position; and

means on said flyweight operative to abruptly shift the center ofgravity of said flyweight outward from the flyweight pivot as saidflyweight is moved outward by centrifugal force from its retractedposition to its extended position.

2. A speed control mechanism for a rotary shaft comprising:

a rotary shaft;

drive means connected to said shaft for driving it at a controlledvariable speed;

control means connected to said drive means for varying the driven speedof said shaft;

a flyweight pivoted on said rotary shaft for movement radially outwardunder centrifugal force from a retracted position to an extendedposition and connected to said control means for controlling saidcontrol means in response to the radial movement of said flyweight; and

means on said flyweight operative to abruptly shift the center ofgravity of said flyweight outward from the flyweight pivot as saidflyweight is moved outward by centrifugal force from its retractedposition to its extended position.

3. A speed control mechanism for a rotary shaft cornprising:

a rotary shaft;

drive means connected to said shaft for driving it at a controlledvariable speed;

control means connected to said drive means for varying the driven speedof said shaft;

a flyweight pivoted on said rotary shaft for movement radially outwardunder centrifugal force from a retracted position to an extendedposition and connected to said control means for controlling saidcontrol means in response to the radial movement of said flyweight; and

means on said flyweight for abruptly changing the magnitude of torquecaused by centrifugal force acting on the flyweight as the flyweightmoves between its retracted and extended positions.

4. A speed control mechanism for a rotary shaft comprising a rotaryshaft;

drive means connected to said shaft for driving it at a controlledvariable speed;

control means connected to said drive means for varying the driven speed:of said shaft;

a fly weight pivoted on said rotary shaft for movement radially outwardunder centrifugal force from a retrncted position toward an extendedposition and connected to said control means for controlling saidcontrol means in response to the radial movement of said flyweight;

an elongated closed bore provided in said flyweight with one end of saidbore being substantially closer to the pivot of said fiyweight than theother end of said bore;

said bore also being located in said flyweight so that said other end ofsaid bore is located closer to the axis of said shaft than the one endof said bore in the retracted position of said flyweight;

said bore being located so that in the extended position of saidflyweight the one end of said bore is located closer to said shaft axisthan said other end of said bore; and

an inner weight movably contained in said bore for movement between theopposite ends of said bore wherein in the retracted position of said flyweight, centrifugal force maintains said inner weight at said one end ofsaid bore and as said fiyweight moves to its extended position, the boreeventually moves to a position wherein centrifugal force moves saidinner weight to the other end of said bore to shift the center ofgravity of the fiyweight away from the flyweight pivot, thus increasingthe torque of the centrifugal force acting on said fiyweight.

5. The combination of claim 4 wherein:

said flyweight is pivoted on said shaft to move in a plane parallel tothe shaft axis.

6. The combination of claim 4 including:

a relatively weak spring located in said bore biasing the inner weighttoward said one end of said bore.

References Cited UNITED STATES PATENTS 723,196 3/1903 Dysterud 73-538771,771 10/1904 Dysterud 73521 2,422,733 6/ 1947 Jimerson 91-762,646,978 7/1953 Barnes 73536 2,906,833 9/1959 Lon-g 73-550 3,071,1151/1963 Schott 91-76 3,279,485 10/1966 Alexander 13757 FOREIGN PATENTS467,506 8/1950 Canada.

CAR-ROLL B. DORITY, JR., Primary Examiner.

